Question

How do you solve \[xy-3x=40\]; \[x=5\]?

Answer 1

Hint: This question is from the topic of algebra. In this question, we will find the value of y. In solving this question, we will put the value of x as 5 (as it is given in the question) in the equation \[xy-3x=40\]. After putting the value of x, we will solve the further question. After solving the further question, we will find the value of y. After that, we will see the alternate method to solve this question.

Complete step-by-step answer:
Let us solve this question.
In this question, we will find the value of y using the given equations. The equations are: \[xy-3x=40\] and \[x=5\].
So, we have given that the value of x is 5. And, we have given another equation as
\[xy-3x=40\]
Now, we will put the value of x as 5 in the above equation. After putting the value of x, we can write the above equation as
\[5\times y-3\times 5=40\]
The above equation can also be written as
\[\Rightarrow 5y-3\times 5=40\]
The above equation can also be written as
\[\Rightarrow 5y-15=40\]
Now, we will take the term 15 to the right side of the equation. We can write the above equation as
\[\Rightarrow 5y=40+15\]
We can write the above equation as
 \[\Rightarrow 5y=55\]
Now, we will divide 5 to the both sides of the equation.
\[\Rightarrow \dfrac{5y}{5}=\dfrac{55}{5}\]
The above can also be written as
\[\Rightarrow y=11\]
So, we have solved this question and find the value of y as 11.

Note: We should have a better knowledge in the topic of algebra to solve this type of question easily. We can solve this question by different way.
Let us first solve the equation
\[xy-3x=40\]
By dividing x to the both side of equation, we can write the above equation as
\[\Rightarrow \dfrac{\left( xy-3x \right)}{x}=\dfrac{40}{x}\]
The above equation can also be written as
\[\Rightarrow \dfrac{x\left( y-3 \right)}{x}=\dfrac{40}{x}\]
\[\Rightarrow y-3=\dfrac{40}{x}\]
We can write the above equation as
\[\Rightarrow y=\dfrac{40}{x}+3\]
Now, we will put the value of x as 5 in the above equation. We can write the above equation as
\[\Rightarrow y=\dfrac{40}{5}+3=8+3\]
\[\Rightarrow y=11\]
We have got the same answer, so we can use this method too.